The present invention relates to a process for manufacturing cold-formed shaped packaging from a metal plastic-laminate in which the laminate is held between a retaining tool and a die exhibiting at least one opening, and a stamping tool is driven into the die opening causing the laminate to be formed into shaped packaging with one or more recesses, the die and the retaining tool each exhibit a facing edge region, the die features within the edge region a shoulder region that surrounds the die opening or openings and the surface of the shoulder region lies lower than the edge region of the die. The present invention relates also to a device for performing the process of cold forming a metal-plastic laminate into shaped packaging, and relates also to cold formed packaging.
It is known to manufacture shaped packaging such, for example base parts for blister packs, also known as push-through packs, or other packaging containers e.g. by deep drawing, stretch-drawing or thermoforming. The shaped packaging may be manufactured from thermoplastics or from composites or laminates such as e.g. aluminium foils laminated with plastic films or layers of thermoplastics laminated by means of extrusion.
If the shaped-packaging, made by shape-forming, is made from laminates containing metal foils, then shaping tools comprising a stamping tool, a die and a retaining tool may be employed for this purpose. During deformation the laminate is clamped securely between the die and the retaining tool, then the stamping tool moved towards the laminate. As it is lowered, the stamping tool penetrates deeper into the openings in the die thereby deforming the laminate. The flat, laminate is converted into a shaped part exhibiting one or more recesses which are surrounded by shoulders corresponding to the original flat plane of the laminate. Only that part of the laminate in the region of the die opening can flow or be stretched to form a shaped part. In order that the laminate, especially laminates containing metal foil, can be deformed without creating cracks and pores, adequate lateral distance must be maintained between the stamping tool and the die opening. Cold forming a laminate containing a metal foil by this process enables recesses of only small side wall height to be achieved. This results in poor drawing ratios i.e. shallow recesses of large diameter and, therefore, forms of packaging which are too large in relation to the contents.
One possibility for obtaining more laminate for deformation purposes in order to achieve larger wall heights, may be to reduce the retaining force and to employ deep drawing methods. However, as folds would form in the edge or shoulder regions, this type of technology may not be used e.g. for making blister packs from laminates containing metal foil. The edge region and, if desired, the shoulder region of shaped forms of packaging is normally employed for sealing the lid into place. If there are folds present there, then the edge and the shoulders could not be sealed.
The European patent application EP 0 779 143 A1 describes a process for manufacturing such shaped packaging in which a metal-plastic laminate is held securely between a retaining tool and a die featuring one or more openings while two or more stamping tools drive the laminate into the die openings, thereby forming the laminate into shaped packaging with recesses. The process described there consists of two steps. In the first step use is made of a stamping tool that exhibits a high degree of friction in contact with the surfaces effecting the shaping. This causes the laminate to be pre-formed in one or more sub-steps. In a second step a second stamping tool is employed for further shape forming. This stamping tool exhibits a lower degree of friction on the surfaces effecting the shape forming. Using this tool the laminate is shape-formed into its final shape in a series of sub-steps.
The object of the present invention is to provide a process which enables shaped packaging, or shaped parts free of folds, to be made from metal-containing laminates by means of cold forming whereby the degree of forming and size of wall height are an improvement over the state-of-the-art.
That objective is achieved by way of the invention in that a first stamping tool or first stamping tools with a low-friction forming surface pre-form the metal-plastic laminate in a first step up to 100% of the final depth of the recess and, subsequently in a second step, using the first stamping tool or second stamping tool or tools of low-friction forming surface, the pre-formed metal-plastic laminate is shaped up to at least 100% of the final depth of the recesses.
The low degree of friction may be expressed by the dimensionless numbers according to the method 311A in BS 2782. The friction of the stamping tool with respect to the forming surface of the stamping tool is preferably 0.05 to 2.1 e.g. the first or the second and the second tool or second tools for the first and second shaping steps exhibit, at least on the shape-forming surface, different degrees of friction in the region concerned, or the stamping tools exhibit the same friction values.
The first stamping tool or tools may have different geometries from the second stamping tool or tools.
In a preferred version of the invention the first stamping tool or tools is/are driven in a first step down to 90%, usefully to 70% and advantageously to 50% of the final depth of the recesses, and subsequently in a second step the same first stamping tool or tools or a second stamping tool or tools is/are driven down to 100-115%, advantageously to 103-110% of the final depth of the recesses.
The first step, as with the second step, may independent of each other, be divided into two or more strokes of the stamping tool using the same or different tools.
In the present invention the various stamping tools are advantageously employed one after the other and, via pre-forming, each stamping tool is loweredxe2x80x94in a series of steps down maximum depthxe2x80x94into the die opening by the same amount or further than the preceding tool. The metal-plastic laminate springs back, therefore at least the last forming step must exceed the full, i.e. 100% desired depth of deformation.
Usefully, the stamping tools with low-friction forming surface employed in the first step are cylindrical, blunted cone, blunted pyramid or barrel shaped. The stamping tools employed for the second step have the shape of a cone, pyramid, blunted cone, blunted pyramid, segment of a sphere or cap. The stamping tools for the first step feature in particular vertical or steep side walls, and the edges or periphery at the bottom of the tool has a small radius. The stamping tool for the second step with a low-friction forming surface, may be vertical or exhibit sloping side walls, and the transition to the bottom of the stamp may be round or roundish in shape. In the present process the stamping tool or tools, in particular the first tools for the first shaping step, may exhibit between the base of the stamping tool and its side wall an edge radius R of e.g. 0.3 mm to 1.5 mm, preferably 0.5 mm to 1.2 mm. It has also been found useful to vary the geometry of the shape-forming surface of the successive tools. A favourable version in this respect is to gradually increase the value of the edge radius R between the stamping tool base and its side wall on proceeding from the first to the second stamping tool i.e. to round the edges more. Instead of an edge radius R one may introduce in several steps a transition involving conical or blunted cone shaped tools.
It has been found particularly advantageous for a first forming step to employ a first stamping tool having an edge radius R between the tool base and tool side wall of 0.1 mm to 5.0 mm, preferably 0.5 mm to 5.0 mm and a second forming tool for the second forming step having a multi-step conical or blunted cone transition from stamping tool side wall to stamping tool base.
The process according to the invention may be performed e.g. using a die and retaining tool and two or more stamping tools which are lowered one after the other into the openings in a die then raised again. The first and second stamping tools may exhibit on the surfaces effecting forming, the same or different degrees of friction, in each case in the above mentioned region. For pre-forming a first stamping tool e.g. with low-friction forming surface is employed for the first step; this tool is withdrawn and then in the second step the same stamping tool performs the final shape-forming in the same die. For the pre-forming one may e.g. also employ a stamping tool with a low-friction shape forming surface; this tool is withdrawn and a the final shape-forming performed by a second stamping tool, likewise with a low-friction shape-forming surface, introduced into the same die or into a second die after displacing the pre-formed laminate. It is also possible to employ three or more stamping tools with low-friction forming surfaces and this with the same or two different surface geometries or gradually different surface geometries.
In another version the process may be performed such that the stamping tools are arranged coaxial or telescopically inside each other. A first stamping tool with a low-friction forming surface which is ring-shaped in plan view, can effect pre-forming by lowering it into the die. The first stamping tool may be left in the pre-forming position and a second cylindrical-shaped stamping tool, which slides telescopically in the first ring-shaped stamping tool and exhibits a low-friction forming surface, is then lowered effecting the final forming of the laminate. Such stamping tools may be made up of two or more ring-shaped stamping tools and an innermost cylindrical stamping tool all of which slide telescopically inside each other. The degrees of friction of the individual tool surfaces effecting forming may lie in the given range or exhibit the same numerical value.
In another version the process may be performed in such a manner that several dies, in particular two dies with retaining tools, are arranged one after the other and with a stamping tool appointed to each die. Working at a given rhythm the laminate is preformed in a first step in the first die, then the pre-form displaced and in a second step shaped to its final form in the second die. It is also possible to perform the pre-forming in two or more steps and to divide the final shaping operation into two or more steps, with the result that the total number of steps in the process is three, four, etc.
The recesses formed out of the area of laminate material may be cup-shaped, dish-shaped, cap-shaped, barrel-shaped, cylindrical etc. As viewed in plan view, the recesses may be round, oval or polygonal, such as two, three, four, or more cornered. Preferred are recesses with steep to vertical side walls which are as straight as possible and bases which are as domed as little as possible. The recesses are surrounded by a, normally flat, shoulder area of laminate material.
A preferred form of the die is such that the surface of the die shoulder region lies 0.05 to 2 mm, preferably 0.15 to 0.3 mm lower than the surface of the edge region of the die.
The device according to the present invention may contain a die with one or more openings.
Usefully, the device, and therefore the die, exhibits 1 to 200 die openings, preferably 8 to 40 die openings. The deformation of the metal-plastic laminate is effected by at least one stamping tool, which can as such penetrate a die opening. If the die features several openings, then the stamping tool may exhibit a support or support plate or holder plate or the like with a corresponding number of shaping heads attached to it. The stamping tools or shaping heads are dimensioned such that they can penetrate the die openings, forming the metal-plastic laminate in the process. Usefully, the diameter of the stamping tool or shaping heads is 3 to 35% smaller than the diameter of the related die opening, preferably 1 to 15% smaller and in particular 5 to 10% smaller. By the diameter of the stamping tool or shaping head or die opening in the case of a non-circular cross-sectionxe2x80x94such as a convex cross-section e.g. elliptic, oval, polygonal, rectangular, trapezium-shaped, rhomboid shaped etc.,xe2x80x94is meant the smallest diameter.
As a rule, the walls of the openings in the die stand at an angle of 90xc2x0 to the surface of the shoulder region. The edges that the wall of the opening and the surface of the shoulder region form with each other may be rounded with a radius e.g. of 0.1 to 10 mm, usefully 0.1 to 1 mm.
In another preferred version the edge regions of the retaining tool and the die are each 1 to 100 mm wide, usefully 2 to 30 mm and preferably 3 to 20 mm.
The die exhibits the edge region and, within this edge region, the shoulder region. The die openings are arranged in particular symmetrically or also asymmetrically within the shoulder region with the shoulder region forming struts that surround the die openings.
The shoulder region of the die is such that the distances between the edge region of the die and the die openings and between the individual openings are 1 to 50 mm, preferably 5 to 25 mm.
The edge region of the retaining tool or the edge region of the die, or the edge regions of the die and the retaining tool, may exhibit a roughness pattern over part or the whole of the surface there. Typical roughness patterns are corrugations, waffle patterns, embossed patterns, honeycomb patterns, knobs, tooth-like patterns, roughened surfaces etc. Instead of or in addition to the roughness pattern, peripheral strips e.g. of an elastic material such as rubber and the like may be employed.
In the working position the edge regions of the retaining tool and the die usefully lie against the metal-plastic laminate and, if desired with the aid of the roughness pattern, hold the laminate in place such that it cannot be stretched. The shoulder region of the die usefully lies a distance from the parts of the retaining tool facing it; in this region the metal-plastic laminate does not make contact with the retaining tool, and the metal-plastic laminate can be stretched or made to flow according to the degree to which the stamping tool is lowered.
The shoulder regions of the die may be covered wholly or partly with a layer that, at least on the surface, exhibits a low degree of friction. A low degree of friction here means values of 0.05 to 2.1 (dimensionless number), as measured according to method 311A, British Standard 2782. The low friction layer may e.g. contain or be of plastics such as polytetrafluorethylene, polyoxymethylene (polyacetal POM), polyethylene or polyethylene-terephthalate. The low friction layer may also exhibit in mixture form two or more of the plastics mentioned by way of example or one or more of the plastics in mixture form along with hard substances in divided form such as glasses in spherical form. Instead of plastics, other materials may be considered for the low friction layer. This means, for example, metals such as aluminium or chromium steel, especially with polished surfaces. Other low friction layers such as ceramic layers or layers containing graphite, boron nitride or molybdenum disulphide may be employed. The thickness of the low friction layer on the shoulder of the die is not critical as only the surface is of consequence. Under industrial conditions the layer is subjected to large demands with regard to frictional forces and so preference should be given to a thickness that permits some degree of material loss. For that reason the thickness of layer of the above mentioned plastics may be e.g. from 0.5 to 20 mm. The layer of plastic may be inserted in the lowered region of the die as a pre-form, or it may be deposited by spraying, brushing, wiping or some other method of deposition. The plastics may also be deposited for example in a matrix of other materials such as ceramic or metal. Metal layers may be deposited e.g. using chemical or physical methods such as electroplating or electrolytic deposition, plating or vapour deposition in vacuum, or the die may be made, at least in part, of the metals in question.
Stamping tools with low friction surfaces effecting forming comprise as a rule of a retaining device such as a clamping plate and a number of stamping tool heads. Advantageously, the number of stamping tool heads corresponds to the number of die openings. The stamping tool heads penetrate the corresponding opening in the retaining device and the openings in the die.
Stamping tools with low friction surfaces effecting forming are usefully such that at least the shape-forming surface, i.e. the surface of the stamping tool or the shaping heads coming into contact with the laminate, exhibits a low degree of friction. By a low degree of friction in the present case is meant friction valuesxe2x80x94according to method 311A, British Standard 2782xe2x80x94of e.g. 0.05 or less to 2.1 (dimensionless number). At least the low friction surface may contain or be e.g. of metals such as steel, or plastics such as polytetrafluorethylene, polyoxy-methylene polyacetal, (POM), polyethylene-terephthalate, polyethylene, rubber, hard rubber or caoutchoucs, including acrylic polymers. The surfaces of metals may be given the properties to achieve low friction values e.g. by polishing. The stamping tools feature polytetrafluorethylene (Teflon) at least on the shape-forming surfaces. The low friction layer may also exhibit in mixture form two or more of the plastics mentioned by way of example or one or more of the plastics in mixture form and, additionally in divided form, hard substances such as glasses in spherical form. Instead of plastics, other materials may be considered for the low friction layer. This means, for example, metals such as aluminium or chromium steel, especially such with polished surfaces. Other low friction surface layers such as ceramic layers or layers containing graphite, boron nitride or molybdenum disulphide may be employed.
Metal-plastic laminates that may be used are e.g. laminates containing a metal foil which is 8 to 150 xcexcm thick, preferably 20 to 80 xcexcm thick. The foil may be e.g. of steel, iron, copper and preferably aluminium. Included are also metal foils of alloys containing mainly one of the above mentioned metals. Preferred aluminium foils may e.g. be aluminium having a purity of at least 98.0%, usefully 98.3%, advantageously 98.5% and especially 98.6%, the remainder making up the 100% being the accompanying impurities. Further, aluminium foils e.g. of the type AlFeSi or of the AlFeSiMn type may be employed.
The plastics used may be e.g. layers, films or laminates, whereby the foils and laminates may also be oriented, or, in other words, uniaxially or biaxially stretched, be of thermoplastics of the polyolefin, polyamide, polyester, polyvinylchloride type and other types.
Typical examples of thermoplastics of the polyolefin type are polyethylenes such as MDPE, DPE, uni-axially, or biaxially stretched polyethylenes, polypropylenes such as cast polypropylene and uni-axially or biaxially stretched polypropylenes or polyethylene-terephthalate from the polyester series.
The thickness of the thermoplastic in the metal-plastic laminates, whether as layer, film or laminate, may be e.g. 12 to 100 xcexcm, preferably 20 to 60 xcexcm. 
The metal foils and thermoplastics may be converted into a laminate e.g. by adhesive bonding, calandering or extrusion adhesive bonding. In order to join the layers, adhesives and bonding agents may be applied as required and the surfaces to be joined may be modified by a pre-treatment involving plasma, corona or flame treatment methods.
Examples of metal-plastic laminates are laminates having as a first layer e.g. a film or laminate made up of the above mentioned thermoplastics, a second layer, in the form of a metal foil and, on the free side of the metal foil, a third layerxe2x80x94a sealing layer of a polyolefin such as polyethylene or polypropylene or PVC.
Further useable metal-plastic laminates may exhibit a first layer e.g. a film or film-laminate of the above mentioned thermoplastics, a second layer in the form of a metal foil, and a third layer, for example a film or film-laminate or an extruded layer out of one of the above mentioned thermoplastics. Further layers such as sealing layers may be provided.
The metal-plastic laminates may feature a sealing layer in the form of a sealable film or a sealable coating at least on one of the outer lying sides, or on both outer sides. The sealing layer is of necessity the outermost layer in the laminate. In particular the sealing layer may be on one outer side of the laminate, and should be directed towards the contents or shoulder side of the shaped packaging, this in order to enable the lid foil or the like to be sealed into place.
Typical examples of metal-plastic laminates used in practice are:
oPA 25 /Al 45 / PVC 60,
oPA 25 /Al 45 / oPA 25,
Al 120 / PP 50,
oPA 25 / Al 60 / PE 50,
oPA 25 / Al 60 /PP 60,
oPA 25 / Al 45 / PVC 100,
oPA 25 / Al 60 / PVC 60,
oPA 25 / Al 45 / PE-coated,
oPA 25 / Al 45 / oPA 25,
oPA 25 / Al 60 / PVC 100,
oPA 25 / Al 60 / oPA 25 / EAA 5O,
PVC 60 / oPA 25 / Al 60 / PVC 60,
PVC 60 / oPA 15 / Al 45 / oPA 15 / PVC 60,
PVC 60 / oPA 25 / Al 45 /oPA 25 / PVC 60,
oPA 25 / Al 60 / oPVC 30,
oPA 25 / Al 60 / oPVC 60,
oPET 25 / Al 60 / oPVC 30,
oPA 25 / Al 60 / oPET 25,
oPET 25 / Al 60 / oPET 25,
where xe2x80x9coxe2x80x9d stands for xe2x80x9corientedxe2x80x9d, PA for polyamide, PVC for polyvinylchloride, PE for poly-ethylene, PP for polypropylene, PET for polyethylene-terephthalate, EAA for ethyleneacrylic acid and Al for aluminium, and the numbers the thickness of the layer or foil in xcexcm.
The present invention also relates to cold formed packaging manufactured by the process according to the invention where the forms of packaging are made e.g. from one of the above mentioned metal-plastic laminates.
The present invention relates also to the device for performing the process according to the invention in which the dies and the retaining tools exhibit facing edge regions which clamp the laminate between the edge of the die and the edge of the retaining tool such that it cannot stretch, and stamping tools which draw the laminate over the shoulders of the die into the die openings which lie within a shoulder region in the die, the surface of the shoulder region lying 0.01 to 10 mm lower than the edge region of the die, and the laminate slides or flows as it is drawn and/or stretched over the surface of the shoulder region.
Useful is a device for performing the process in which the surface of the shoulder region of the die lies 0.1 to 2.0 mm, preferably 0.15 to 0.3 mm lower than the surface of the edge region of the die.
Preferred is a device for performing the process in which the shoulder regions of the die are partially or wholly covered with a surface layer exhibiting a low friction value of 0.05 to 2.1.
Within the scope of the invention is the use of shaped packaging forms which have been cold formed by the process according to the invention, as container for accommodating individal items in the recesses. Examples of such items are e.g. one, two or three tablets, dragxc3xa9es, pills, ampoules etc. in each recess of a shaped form of packaging such as a blister pack or push-through pack.
The use of the shaped packaging according to the invention includes the individual accommodation of contents in the form of tablets, dragees, pills, capsules, or ampoules having a maximum diameter of 5 to 20 mm, preferably 7 to 10 mm with a maximum height of 1.5 to 10 mm, usefully 3 to 5 mm.
The process according to the invention may be employed for manufacturing, from metal-plastic laminates, cold formed packaging such as base and lid parts of blister packs for pharmaceuticals, foodstuffs and luxury consumables, technical articles, for bases and lids of semi-rigid and rigid packaging for enclosing purposes etc.
On thermoforming plastic films e.g. PVC into blister packs it is possible to achieve high side walls. Up to now, however, it has not been possible to achieve such high side walls on the recesses of shaped forms of packaging such as blister packs made from laminates containing metal foils. This means that the form of packaging that had to be used was much too large in comparison with the contents. It is now possible using the present process to produce shaped forms of packaging that do not exhibit the disadvantages experienced to date i.e. such as the low wall height compared to that achieved with thermoformed plastic films. With the present process it is now possible to manufacture shaped forms of packaging which with respect to size of packaging, are at least comparable. The packaging can therefore be designed to look more attractive and to have a better image from the ecological standpoint. At the same time the pore-free depth achieved by shape forming can also be improved.
Drawing ratiosxe2x80x94i.e. a ratio of diameter to the depth of the recess formedxe2x80x94of e.g. 1.9 to 5 or preferably 2.1 to 2.6 can be achieved. The diameter of the recess, if not round in cross-section, is to be understood as the largest diameter i.e. in the case of non-circular cross-sections, such as a convex cross-section e.g. elliptical, oval, polygonal, rectangular, trapezium shaped, rhomboid etc.
The number of recesses in each base part is not critical and may e.g. be one, two or more. In pharmaceutical applications packs with 6 to 40 recesses are normal.
By cold forming is meant here forming at temperatures of e.g. 10 to 35xc2x0 C., preferably 20 to 30xc2x0 C.
The laminates that are processed into shaped forms of packaging such as blister packs and in particular the bases of blister packs remain pore-free even at high drawing ratios, and the reject rate due to forming is substantially reduced.